diff --git a/src/DataWrangling/inpainting.jl b/src/DataWrangling/inpainting.jl
index dde0f1f91..a081fa1d7 100644
--- a/src/DataWrangling/inpainting.jl
+++ b/src/DataWrangling/inpainting.jl
@@ -51,7 +51,12 @@ function propagate_horizontally!(inpainting::NearestNeighborInpainting, field, m
         iter += 1
     end
 
-    launch!(arch, grid, size(field), _fill_nans!, field)
+    # Fill any remaining NaN values with the mean of valid data.
+    # Using 0 would be catastrophic for fields like salinity (~34 psu).
+    valid_sum = sum(x -> ifelse(isnan(x), zero(x), x), field; condition=interior(mask))
+    valid_count = sum(x -> !isnan(x), field; condition=interior(mask))
+    fill_value = convert(eltype(field), valid_sum / valid_count)
+    launch!(arch, grid, size(field), _fill_nans!, field, fill_value)
     fill_halo_regions!(field)
 
     return field
@@ -80,7 +85,7 @@ end
     end
 
     FT_NaN = convert(FT, NaN)
-    @inbounds substituting_field[i, j, k] = ifelse(value == 0, FT_NaN, value / donors)
+    @inbounds substituting_field[i, j, k] = ifelse(donors == 0, FT_NaN, value / donors)
 end
 
 @kernel function _substitute_values!(field, substituting_field)
@@ -97,9 +102,9 @@ end
     @inbounds field[i, j, k] = ifelse(mask[i, j, k], FT_NaN, field[i, j, k])
 end
 
-@kernel function _fill_nans!(field)
+@kernel function _fill_nans!(field, fill_value)
     i, j, k = @index(Global, NTuple)
-    @inbounds field[i, j, k] *= !isnan(field[i, j, k])
+    @inbounds field[i, j, k] = ifelse(isnan(field[i, j, k]), fill_value, field[i, j, k])
 end
 
 """
diff --git a/test/runtests_setup.jl b/test/runtests_setup.jl
index b3e0fae9d..77ff379a1 100644
--- a/test/runtests_setup.jl
+++ b/test/runtests_setup.jl
@@ -309,7 +309,8 @@ function test_inpainting_algorithm(arch, dataset, start_date, inpainting;
         partially_inpainted_interior = on_architecture(CPU(), interior(partially_inpainted_field))
 
         @test all(fully_inpainted_interior .!= 0)
-        @test any(partially_inpainted_interior .== 0)
+        # Partially inpainted data should have no NaN (remaining NaN is filled with the field mean)
+        @test !any(isnan.(partially_inpainted_interior))
     end
     return nothing
 end